Ramprasad Ravichandran

Multi-layer floorplanning for reliable system-on-package

Physical design automation for the new emerging mixed-signal system-on-package (SOP) technology requires a new kind of floorplanner - it must place both active components such as digital IC, analog ICs, memory modules, MEMS, and optoelectronic modules, and embedded passive components such as capacitors, resistors and inductors in a multi-layer packaging substrate while considering various signal integrity issues. We propose a new interconnect-centric multi-layer floorplanner named MF-SOP, which is based on a multiple objective stochastic simulated annealing method. The contribution of this work is to first formulate this new kind of floorplanning problem and then to develop an effective algorithm that handles various design constraints unique to SOP. The related experiments show that the area reduction of MF-SOP compared to its 2D counterpart is on the order of O(k) and wirelength reduction is 39% average for k-layer SOP, while satisfying design constraints.

Eliminating wire crossings for molecular quantum-dot cellular automata implementation

When exploring computing elements made from technologies other than CMOS, it is imperative to investigate the effects of physical implementation constraints. This paper focuses on molecular quantum-dot cellular automata circuits. For these circuits, it is very difficult for chemists to fabricate wire crossings (at least in the near future). A novel technique is introduced to remove wire crossings in a given circuit to facilitate the self assembly of real circuits - thus providing meaningful and functional design targets for both physical and computer scientists. The technique eliminates all wire crossings with minimal logic gate/node duplications. Experimental results based on existing QCA circuits and other benchmarks are quite encouraging, and suggest that further investigation is needed.

Fabricatable Interconnect and Molecular QCA Circuits

When exploring computing elements made from technologies other than complementary metal-oxide-semiconductor, it is imperative to investigate circuits and systems assuming realistic physical implementation constraints. This paper looks at molecular quantum-dot cellular automata (QCA) devices within this context. With molecular QCA, physical coplanar wire crossings may be very difficult to fabricate in the near to midterm. Here, we consider how this will affect interconnect. We introduce a novel technique to remove wire crossings in a given design in order to facilitate the self-assembly of real circuits - thus, providing meaningful and functional design targets for both physical and computer scientists. The proposed methodology eliminates all wire crossings with minimal logic gate/node duplications. Simulation results based on existing QCA circuits and other benchmarks are presented, and suggest that further investigation is needed.

Value-based action selection for exploration and dynamic target observation with robot teams

Move Value Estimation for Robot Teams (MVERT) is a robot action selection algorithm for teams performing multiple competing tasks. The goal of MVERT is to select actions for robot team members to maximize the teams joint utility toward overall mission progress in a computationally efficient manner. MVERT is fully distributed, with each robot using information about other teammates to select its action with the greatest value. MVERT selects actions for a robot team to perform multi-task exploration and dynamic target observation. Successful action selection is demonstrated in simulation for exploration and in simulation and on robots for dynamic target observation.

Automatic cell placement for quantum-dot cellular automata

Quantum-dot Cellular Automata (QCA) is a novel computing mechanism that can represent binary information based on spatial distribution of electron charge configuration in chemical molecules. It has the potential to allow for circuits and systems with functional densities that are better than end of the roadmap CMOS, but also imposes new constraints on system designers. In this paper we develop the first cell-level placement of QCA circuits, where the given circuit is assumed to be partitioned into 4-phase asynchronous QCA timing zones. We formulate the QCA cell placement in each timing zone as a unidirectional geometric embedding of k-layered bipartite graphs. We then present an analytical and a stochastic solution for minimizing the wire crossings and wire length in these placement solutions.

Physical layout automation for system-on-packages

System-On-Package (SOP) technology provides a capability to integrate both mixed-signal active components and passive components all into a single high speed/density three dimensional packaging substrate. The physical layout resource of SOP is multi-layer in nature, where all layers are used for both placement and routing unlike the traditional multi-layer PCB or MCM packaging. In this paper, we present the first 3D physical design algorithms targeting SOP technology. 3D partitioning divides the input design into multiple layers. 3D placement determines the location of the active and passive components in multi-layer packaging substrate while considering various signal integrity issues. 3D global routing performs the following major steps: pin/net distribution, layer assignment, tree generation, and channel/pin assignment. Our experimental results demonstrate the effectiveness of our approaches.

Using circuits and systems-level research to drive nanotechnology

This paper details nano-scale devices being researched by physical scientists to build computational systems. It also reviews some existing system design work that uses the devices to be discussed. It concludes with a discussion of how the authors believe system-level research can best be used to positively affect actual device development. This work has led to a more thorough design methodology that address whether or not computationally interesting and buildable circuits are possible with the quantum-dot cellular automata (QCA), while also providing significant wins over end-of-the-roadmap CMOS.

Improving Multirobot Multitarget Tracking by Communicating Negative Information

In this paper, we consider the sensor fusion problem for a team of robots, each equipped with monocular color cameras, cooperatively tracking multiple ambiguous targets. In addition to coping with sensor noise, the robots are unable to cover the entire environment with their sensors and may be out numbered by the targets. We show that by explicitly communicating negative information (i.e. where robots don’t see targets), tracking error can be reduced significantly in most instances. We compare our system to a baseline system and report results.